Such sensors are mostly used in the area of hydraulics to reproducibly measure pressures of a few tens to hundreds of bars. Such sensors must have an extremely stable and durable design, be corrosion-resistant and reliable from the safety point of view.
A particularly large number of high-pressure sensors is used in the automotive industry for direct gasoline injection, common-rail direct diesel injection, and in the hydraulic system of the electronic stability program.
In each of these cases, absolute reliability during use, reproducibly accurate measurement, fail-safe operation, temperature stability, and low price are essential.
For the above-named applications, the use of high-pressure sensor elements having piezoresistive functional layers made of NiCrSi alloys has been proposed. It has also been proposed that such sensor elements be bonded to an analyzer circuit situated in the high-pressure sensor device itself, thus providing a high-pressure sensor device capable of being connected to a hydraulic pressure space while delivering a preprocessed output signal.
The present invention relates to a high-pressure sensor device having a pressure sensor element and an electric circuit, in particular in the form of a semiconductor component, the pressure sensor element having a membrane which is deformable under the effect of pressure, and a functional layer which, when deformed, experiences a change in its electrical properties and has at least one electric terminal area.
In high-pressure sensor devices of this type, the above-mentioned object is achieved according to the present invention by connecting the electric circuit directly to the electric terminal area using a solder layer.
It has been proposed for existing high-pressure sensor devices that electric signals, i.e., measured quantities, of the functional layer be conducted to the appropriate analyzer circuit with the aid of bonding wires or spring contact elements or conductors integrated in flexible films. The analyzer circuit is then situated in the housing of the high-pressure sensor device independently of the pressure sensor element and is connected thereto as described with the aid of a flexible electrical connection. The analyzer circuit typically contains a PC board or a hybrid structure, at least one integrated circuit in the form of a semiconductor chip being provided with a complex part of the analyzer circuit. Further circuit elements in discrete design which are responsible for optimizing the electromagnetic properties of the high-pressure sensor device may be additionally provided within the housing.
Such a design, however, requires a plurality of manufacturing steps such as the installation of the high-pressure sensor element, the installation of the analyzer circuit, and the electric connection of these two components.